Examples/Filtering/ResampleImageFilter8.cxx

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//  Software Guide : BeginLatex
//
//  The following example illustrates how to use the
//  \doxygen{WindowedSincInterpolateImageFunction} for resampling an image.
//  This interpolator is in theory the best possible interpolator for
//  reconstructing the continuous values of a discrete image. In the spectral
//  domain, this interpolator is performing the task of masking the central
//  part of the spectrum of the sampled image, that in principle corresponds
//  to the spectrum of the continuous image before it was sampled into a
//  discrete one. In this particular case an \doxygen{AffineTransform} is used
//  to map the input space into the output space.
//
//  \index{itk::AffineTransform!resampling}
//
//  Software Guide : EndLatex
 
 
#include "itkImage.h"
#include "itkImageFileReader.h"
#include "itkImageFileWriter.h"
#include "itkResampleImageFilter.h"
#include "itkConstantBoundaryCondition.h"
#include "itkWindowedSincInterpolateImageFunction.h"
 
 
//  Software Guide : BeginLatex
//
//  The header of the affine transform is included below.
//
//  Software Guide : EndLatex
 
// Software Guide : BeginCodeSnippet
#include "itkAffineTransform.h"
// Software Guide : EndCodeSnippet
 
 
int
main(int argc, char * argv[])
{
  if (argc < 4)
  {
    std::cerr << "Usage: " << std::endl;
    std::cerr << argv[0] << "  inputImageFile  outputImageFile  degrees"
              << std::endl;
    return EXIT_FAILURE;
  }
 
  constexpr unsigned int Dimension = 2;
  using InputPixelType = unsigned char;
  using OutputPixelType = unsigned char;
 
  using InputImageType = itk::Image<InputPixelType, Dimension>;
  using OutputImageType = itk::Image<OutputPixelType, Dimension>;
 
  using ReaderType = itk::ImageFileReader<InputImageType>;
  using WriterType = itk::ImageFileWriter<OutputImageType>;
 
  auto reader = ReaderType::New();
  auto writer = WriterType::New();
 
  reader->SetFileName(argv[1]);
  writer->SetFileName(argv[2]);
 
  const double angleInDegrees = std::stod(argv[3]);
 
  //  Software Guide : BeginLatex
  //
  //  The Resampling filter is instantiated and created just like in previous
  //  examples. The Transform is instantiated and connected to the resampling
  //  filter.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using FilterType =
    itk::ResampleImageFilter<InputImageType, OutputImageType>;
 
  auto filter = FilterType::New();
 
  using TransformType = itk::AffineTransform<double, Dimension>;
 
  auto transform = TransformType::New();
 
  filter->SetTransform(transform);
  // Software Guide : EndCodeSnippet
 
  //  Software Guide : BeginLatex
  //
  //  The salient feature of this example is the use of the
  //  \doxygen{WindowedSincInterpolateImageFunction}, which uses a truncated
  //  \emph{sinc} function in order to interpolate the resampled image.
  //
  //  There is a close relationship between operations performed in the
  //  spatial domain and those applied in the spectral domain. For example,
  //  the action of truncating the \emph{sinc} function with a box function in
  //  the spatial domain will correspond to convolving its spectrum with the
  //  spectrum of a box function. Since the box function spectrum has an
  //  infinite support on the spectral domain, the result of the convolution
  //  will also have an infinite support on the spectral domain. Due to this
  //  effects, it is desirable to truncate the \emph{sinc} function by using a
  //  window that has a limited spectral support. Many different windows have
  //  been developed to this end in the domain of image processing. Among the
  //  most commonly used we have the \textbf{Hamming} window. We use here a
  //  Hamming window in order to define the truncation of the sinc function.
  //  The window is instantiated and its type is used in the instantiation of
  //  the WindowedSinc interpolator. The size of the window is one of the
  //  critical parameters of this class. The size must be decided at
  //  compilation time by using a \code{const integer} or an \code{enum}.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  using BoundaryConditionType =
    itk::ConstantBoundaryCondition<InputImageType>;
 
  constexpr unsigned int WindowRadius = 5;
 
  using WindowFunctionType =
    itk::Function::HammingWindowFunction<WindowRadius>;
 
  using InterpolatorType =
    itk::WindowedSincInterpolateImageFunction<InputImageType,
                                              WindowRadius,
                                              WindowFunctionType,
                                              BoundaryConditionType,
                                              double>;
 
  auto interpolator = InterpolatorType::New();
 
  filter->SetInterpolator(interpolator);
 
  filter->SetDefaultPixelValue(100);
  // Software Guide : EndCodeSnippet
 
 
  //  Software Guide : BeginLatex
  //
  //  The parameters of the output image are taken from the input image.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  reader->Update();
  const InputImageType::SpacingType & spacing =
    reader->GetOutput()->GetSpacing();
  const InputImageType::PointType & origin = reader->GetOutput()->GetOrigin();
  const InputImageType::DirectionType & direction =
    reader->GetOutput()->GetDirection();
  InputImageType::SizeType size =
    reader->GetOutput()->GetLargestPossibleRegion().GetSize();
  filter->SetOutputOrigin(origin);
  filter->SetOutputSpacing(spacing);
  filter->SetOutputDirection(direction);
  filter->SetSize(size);
  // Software Guide : EndCodeSnippet
 
 
  filter->SetInput(reader->GetOutput());
  writer->SetInput(filter->GetOutput());
 
 
  TransformType::OutputVectorType translation1;
 
  const double imageCenterX = origin[0] + spacing[0] * size[0] / 2.0;
  const double imageCenterY = origin[1] + spacing[1] * size[1] / 2.0;
 
  translation1[0] = -imageCenterX;
  translation1[1] = -imageCenterY;
 
  transform->Translate(translation1);
 
 
  std::cout << "imageCenterX = " << imageCenterX << std::endl;
  std::cout << "imageCenterY = " << imageCenterY << std::endl;
 
 
  const double degreesToRadians = std::atan(1.0) / 45.0;
  const double angle = angleInDegrees * degreesToRadians;
  transform->Rotate2D(-angle, false);
 
 
  TransformType::OutputVectorType translation2;
  translation2[0] = imageCenterX;
  translation2[1] = imageCenterY;
  transform->Translate(translation2, false);
 
 
  //  Software Guide : BeginLatex
  //
  //  The output of the resampling filter is connected to a writer and the
  //  execution of the pipeline is triggered by a writer update.
  //
  //  Software Guide : EndLatex
 
  // Software Guide : BeginCodeSnippet
  try
  {
    writer->Update();
  }
  catch (const itk::ExceptionObject & excep)
  {
    std::cerr << "Exception caught !" << std::endl;
    std::cerr << excep << std::endl;
  }
  // Software Guide : EndCodeSnippet
 
  return EXIT_SUCCESS;
}